Introduction

JRE (Java Runtime Environment). This is the subset of
Oracle’s JDK (Java Development Kit) that you can ship with your application. It is free.

The JRE, described here, is for people who just want
to run Java programs or browse Applets on the web. You must use the much larger
JDK if you want to write your own Java
programs. You don’t need both.

Which Java.exe?

When you install multiple JREs (Java Runtime Environments)and JDKs (Java Development Kits)
you will have many different java.exe, javaw.exe, javaws.exe and javac.exe installed. Which one
is used depends on which JREs
and JDKs
you have installed, which JVMs are enabled in the Java Control Panel, the SET JAVA_HOME, the path, the current directory and the phases of moon used in a pseudo random
number generator to select one of the installed Javas. Verify you are using what you expect with java.exe-version.

Downloading the JRE

You can find the various downloads with your browser. For
Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64, make sure you are logged in
as an administrator before you install. Some suggest it is best also to turn on
UAC (User Account Control)
(that irritating Visa User Account control) during the install. The downloads are
labelled as updates, but they are complete in themselves. You don’t need to
install a previous version.

Below is how to get Java for Windows, Linux and Solaris. For other platforms (e.g.
various Unices) see your OS (Operating System)
vendor’s site. For example for NetBSD Unix Java is included in pkgsrc (the
Packages System).

A staticJRE
is one kept on an old version without upgrading it to test software on old the old
version.

Where and how to download various Java JREs

Version

Executables

Notes

JRE 1.8.0_11253MB self-installing executable. Includes JavaFX.

You will get one JRE
automatically installed as a side effect of installing the
JDK.

Look for the third
entry, Java JRE
8 Then click Download. Then select your
platform tick the licence agreement and Click Windows
Offline Installation. This is most likely the
version you want to download.
For W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32, W10-64, Linux, LinuxARM, LinuxX86, LinuxX64, Ubuntu, Solaris, SolarisSPARC, SolarisSPARC64, SolarisX86, SolarisX64 and OSX, make sure
you are logged in as an administrator before you install. The install will
work more smoothly if you launch the install of the download with
run as administrator and if you have
UAC
turned on. If you have 64-bit Windows, you probably
want to install both the 64 and 32-bit versions of Java. Often there are two releases posted. Make sure you pick the one
you want.

The download includes the Java Plug-in for Applets and Java Web Start. It
includes the JVM (Java Virtual Machine)
and the standard class library files, but no source and no javac.exe. It does not include JavaMail or JAF. It
will install in C:\Program Files\java\jre1.8.0_112\. If you want to
write your own Java programs, install the JDK instead.

To get any older version, you must sign up for a support contract.

You might want to manually set your JAVA_HOME
environment variable to the JRE
directory e.g. C:\Program Files\java\jre1.8.0_112\. Some software
finds Java using this variable rather than poking around in the registry. If you have
a JDK
at well set JAVA_HOME to point to it.

Polishing and Testing Your JRE

Testing your JRE
is more complicated that you might expect. You want to find out if Java is working
properly on the desktop and in each of your browsers. Further, you want to test that
Java Web Start is working properly on the desktop and in each of your browsers. Just
because Java/Java Web Start works in one browser, does not mean it will automatically
work in another.

Click start ⇒ Control
Panel ⇒ Java. Make sure all your JREs/JDKs
are registered there. If not ask it to find and register them. Remove any JREs/JDKs
you are not using.

Configure your set environment for the CLASSPATH.
If you are not sure use CLASSPATH=. See environment for details of how. See classpath for details.

Copy your various library jars into the C:\Program Files\java\jre1.8.0_112\\lib\ext\ directory.

If you have Windows 7 64-bit, you will need to
install two JRE
s, a 64-bit one in C:\Program
Files\java\jre1.8.0_112 for used by your desktop apps and by your
64-bit browsers and a 32-bit
one in C:\Program Files (x86)\java\jre1.8.0_112 for use
by your 32-bit browsers.

Sooner or later you will have to reinstall the JDK/JRE and you will lose your ext directories. You can quickly rebuild them if you maintain a bat file like this and run
it after every JRE/JDK install. Adjust the file to account for where your ext dirs are and where the jars are you need.

In Internet Explorer, make sure all three boxes under Tools
Internet option ⇒ Advanced ⇒ Microsoft VM are checked.

In Internet Explorer 7+, you must OK allow blocked content permission
to run Active X on the site, (even your own when running offline). This also gives
permission to run Java. Since Java is perfectly safe because it runs it a sandbox,
logically it should not need special permission. This roadblock to Java is just
part of Microsoft’s war on Oracle and Java.

Test

java.exe -version

You should see the
expected version you just installed, probably 1.8.0_112. It can be problematic to have more than one version
installed at a time.

It should tell you that your browser is using the JVM
version you just installed, probably 1.8.0_112. Look for the line marked java.version. If Wassup does not run, or
you have the wrong version, go into Settings ⇒ Control
Panel ⇒ Java Plug-In ⇒ Browser and turn off each browser, then
click apply, then turn them on again, then hit
apply again. Then retest with Wassup. If that still does not work, turn on the Java
console, try Wassup again and
look for clues.

Test Java Web Start on the
desktop by typing javaws.exe and running any sample
application.

Check that the associations for the *.jnlp extension
is set to point to the appropriate javaws.exe and
*.jar is set to point to javaw.exe.

The associations for *.jar and *.jnlp are fragile. They mysteriously change to obsolete versions, or javaw.exe version without a console or even unrelated programs like Winzip.exe. Using the java.exe-jarmyjar.jar syntax in your bat/btm files rather is more robust than myjar.jar. It works even when the associations are
corrupted.

Set up associations for *.jar files to make them
double clickable, following the instructions here. By default the association will be set up to
javaw.exe and you won’t see any output.

Check that Java Web Start is working in each browser by testing SetClock. Click SetClock to test.

Check the Opera browser’s quick preferences to make sure you have Java
enabled. Turn on the console with tools ⇒ advanced ⇒
Java console to get some hints why it may not be working. Make sure Opera
has *.jnlp files associated with mime type application-x-java-jnlp-file in preferences ⇒
files.

Silent JRE
Installs

If you want to install the JRE
on many machines, or an install triggered by an utter novice, you would prefer a
command-line style install that did not ask any questions as it progressed. That is
called a silent install. It does not mean stealthily
installing the JRE
or other app on a machine without the owner’s notice.

Learning More

Linux

Installing a JRE
under Linux is much more complicated that under Windows. You need to perform half a
dozen manual installation steps. You also need to set up a soft link from each of
your browser plug-ins to the corresponding Java *.so
libraries. Download and study the install instructions. You will never guess them.
Consult your browser for documentation on the soft links.

Android

There is no JRE
for Android. If you want to run Java ME applications on Android, you need to convert
your jars to the format that Android understands. For that purpose you can use a tool
such as Java/J2ME Runner.

Multiple JRE
s

If you want to install multiple JRE
s, first uninstall all your JDKs
and JRE
s, then install the JREs
and JDKs
the oldest version first and install them in order. If you want the
JDK, there in no
need to install the corresponding JRE
as well.

Then instead of saying java.exe, use the fully qualified
name to select which version of the java run time you want e.g. C:\Program Files\java\jre1.8.0_112\ \bin\java.exe.